Buggy code:
public class DeltaProcessor { static class OutputsInfo { int outputCount ; IPath [ ] paths ; int [ ] traverseModes ; OutputsInfo ( IPath [ ] paths , int [ ] traverseModes , int outputCount ) { } public String toString ( ) { } } static class RootInfo { char [ ] [ ] inclusionPatterns ; char [ ] [ ] exclusionPatterns ; JavaProject project ; IPath rootPath ; int entryKind ; IPackageFragmentRoot root ; RootInfo ( JavaProject project , IPath rootPath , char [ ] [ ] inclusionPatterns , char [ ] [ ] exclusionPatterns , int entryKind ) { } IPackageFragmentRoot getPackageFragmentRoot ( IResource resource ) { } boolean isRootOfProject ( IPath path ) { } public String toString ( ) { } } private static final int IGNORE = 0 ; private static final int SOURCE = 1 ; private static final int BINARY = 2 ; private static final String EXTERNAL_JAR_ADDED = "external<seq2seq4repair_space>jar<seq2seq4repair_space>added" ; private static final String EXTERNAL_JAR_CHANGED = "external<seq2seq4repair_space>jar<seq2seq4repair_space>changed" ; private static final String EXTERNAL_JAR_REMOVED = "external<seq2seq4repair_space>jar<seq2seq4repair_space>removed" ; private static final String EXTERNAL_JAR_UNCHANGED = "external<seq2seq4repair_space>jar<seq2seq4repair_space>unchanged" ; private static final String INTERNAL_JAR_IGNORE = "internal<seq2seq4repair_space>jar<seq2seq4repair_space>ignore" ; private static final int NON_JAVA_RESOURCE = - 1 ; public static boolean DEBUG = false ; public static boolean VERBOSE = false ; public static boolean PERF = false ; public static final int DEFAULT_CHANGE_EVENT = 0 ; public static long getTimeStamp ( File file ) { } private DeltaProcessingState state ; JavaModelManager manager ; private JavaElementDelta currentDelta ; private Openable currentElement ; public ArrayList javaModelDeltas = new ArrayList ( ) ; public HashMap reconcileDeltas = new HashMap ( ) ; private boolean isFiring = true ; private final ModelUpdater modelUpdater = new ModelUpdater ( ) ; public HashSet projectCachesToReset = new HashSet ( ) ; public Map oldRoots ; private HashSet rootsToRefresh = new HashSet ( ) ; public int overridenEventType = - 1 ; private SourceElementParser sourceElementParserCache ; public HashMap classpathChanges = new HashMap ( ) ; public DeltaProcessor ( DeltaProcessingState state , JavaModelManager manager ) { } public ClasspathChange addClasspathChange ( IProject project , IClasspathEntry [ ] oldRawClasspath , IPath oldOutputLocation , IClasspathEntry [ ] oldResolvedClasspath ) { } private void addDependentProjects ( IJavaProject project , HashMap projectDependencies , HashSet result ) { } private void addToParentInfo ( Openable child ) { } private void addToRootsToRefreshWithDependents ( IJavaProject javaProject ) { } private void checkProjectsBeingAddedOrRemoved ( IResourceDelta delta ) { } private void checkProjectReferenceChange ( IProject project , JavaProject javaProject ) { } private void readRawClasspath ( JavaProject javaProject ) { } private void checkSourceAttachmentChange ( IResourceDelta delta , IResource res ) { } private void close ( Openable element ) { } private void contentChanged ( Openable element ) { } private Openable createElement ( IResource resource , int elementType , DeltaProcessor . RootInfo rootInfo ) { } public void checkExternalArchiveChanges ( IJavaElement [ ] elementsScope , IProgressMonitor monitor ) throws JavaModelException { if ( ( monitor != null ) && ( monitor . isCanceled ( ) ) ) throw new OperationCanceledException ( ) ; try { if ( monitor != null ) monitor . beginTask ( "" , 1 ) ; for ( int i = 0 , length = elementsScope . length ; i < length ; i ++ ) { this . state . addForRefresh ( elementsScope [ i ] ) ; } HashSet elementsToRefresh = this . state . removeExternalElementsToRefresh ( ) ; <START_BUG> boolean hasDelta = createExternalArchiveDelta ( elementsToRefresh , monitor ) ; <END_BUG> if ( hasDelta ) { IJavaElementDelta [ ] projectDeltas = this . currentDelta . getAffectedChildren ( ) ; final int length = projectDeltas . length ; final IProject [ ] projectsToTouch = new IProject [ length ] ; for ( int i = 0 ; i < length ; i ++ ) { IJavaElementDelta delta = projectDeltas [ i ] ; JavaProject javaProject = ( ( JavaProject ) ( delta . getElement ( ) ) ) ; projectsToTouch [ i ] = javaProject . getProject ( ) ; } IWorkspaceRunnable runnable = new IWorkspaceRunnable ( ) { public void run ( IProgressMonitor progressMonitor ) throws CoreException { for ( int i = 0 ; i < length ; i ++ ) { IProject project = projectsToTouch [ i ] ; if ( JavaBuilder . DEBUG ) System . out . println ( ( ( "Touching<seq2seq4repair_space>project<seq2seq4repair_space>" + ( project . getName ( ) ) ) + "<seq2seq4repair_space>due<seq2seq4repair_space>to<seq2seq4repair_space>external<seq2seq4repair_space>jar<seq2seq4repair_space>file<seq2seq4repair_space>change" ) ) ; project . touch ( progressMonitor ) ; } } } ; try { ResourcesPlugin . getWorkspace ( ) . run ( runnable , monitor ) ; } catch ( CoreException e ) { throw new JavaModelException ( e ) ; } if ( ( this . currentDelta ) != null ) { this . fire ( this . currentDelta , DeltaProcessor . DEFAULT_CHANGE_EVENT ) ; } } } finally { this . currentDelta = null ; if ( monitor != null ) monitor . done ( ) ; } } private boolean createExternalArchiveDelta ( HashSet refreshedElements , IProgressMonitor monitor ) { } private JavaElementDelta currentDelta ( ) { } private void deleting ( IProject project ) { } private void elementAdded ( Openable element , IResourceDelta delta , DeltaProcessor . RootInfo rootInfo ) { } private void elementRemoved ( Openable element , IResourceDelta delta , DeltaProcessor . RootInfo rootInfo ) { } private int elementType ( IResource res , int kind , int parentType , DeltaProcessor . RootInfo rootInfo ) { } public void flush ( ) { } private SourceElementParser getSourceElementParser ( Openable element ) { } private DeltaProcessor . RootInfo enclosingRootInfo ( IPath path , int kind ) { } public void fire ( IJavaElementDelta customDelta , int eventType ) { } private void firePostChangeDelta ( IJavaElementDelta deltaToNotify , IElementChangedListener [ ] listeners , int [ ] listenerMask , int listenerCount ) { } private void fireReconcileDelta ( IElementChangedListener [ ] listeners , int [ ] listenerMask , int listenerCount ) { }

Fix:
boolean hasDelta = ( elementsToRefresh != null ) && ( createExternalArchiveDelta ( elementsToRefresh , monitor ) ) ;